Self-locking seat belt retractors are generally used in safety belt devices of vehicles in order to roll up a non-emplaced safety belt in a park position and to enable a variable pull-out of the safety belt when it is deployed for restraining an occupant with as little slack as possible. For that purpose, a belt shaft mounted so as to rotate in the seat belt retractor and spring-tensioned in the roll-up (retraction) direction is provided on which the safety belt can be rolled up. In addition, the seat belt retractor may features a blocking (locking) mechanism which is activated when a predetermined extension acceleration of the safety belt (belt-sensitive locking) and/or or of the vehicle (vehicle sensitive locking) is exceeded, so that the belt shaft is blocked at the end in the direction of extension. In a belt-sensitive mechanism, the type of the present invention includes a blocking catch mounted on the belt shaft whose movement is controlled by a disc cam mounted on the belt shaft in a rotational manner. The disc cam itself is spring-tensioned in the belt extension direction of the belt shaft and therefore rotates below the predetermined extension acceleration of the safety belt with the belt shaft. Furthermore, an inertial mass is mounted on the disc cam so as to pivot, and when the predetermined belt extension acceleration is exceeded, said mass is held back and thereby guided into a gearing of the seat belt retractor fixed to the frame and brings the disc cam to a stop against the belt shaft. The blocking mechanism is again activated by the stoppage of the disc cam, in that the blocking catch mounted on the belt shaft executes a guide movement in a gearing fixed to the frame, said movement caused by a guide in a control contour on the disc cam.
The inertial mass must have a certain magnitude because of its above stated mission, since otherwise upon exceeding an extension acceleration it does not stop against the belt shaft. In addition, the inertial mass must be movably mounted on the disc cam rotating with the belt shaft in such a manner that a relative movement with respect to the disc cam must be able to be executed for the control of the blocking device. Because of the mass of the inertial mass and its movable mounting, vibrations acting on the seat belt retractor can result in undesirable noise generated because of the inertial mass.
The object of the invention therefore is to create a self-locking seat belt retractor with a belt-sensitive blocking device having a control sensitive to the belt-strap due to an inertial mass movably mounted on a disc cam which features a reduced generation of noise during vibrations.
To achieve the object the invention proposes a self-locking seat belt retractor with the characteristics of the devices described herein. Other preferred embodiments of the invention can be found in the associated description.